Actinismproof reenforced glass



Patented Oct. 26, 1926.

UNITED-STATES, PATENT OFFICE.

JAMES H. SHEETS, NEWARK, NEW JERSEY, ASSIGNOB TO E I. DU PONT DE INE- MOURS & COM1AI\TY, OF' WILMINGTON, DELAWARE, .A CORPORATION OF DELA- WARE.

' Ne Drawing.

This invention relates to structures composed of laminations of glass and some less fragile material acting as a strengthening means, for example pyroxylin plastic 5 sheeting, i. e. such structures as are popularly called safety glass; and in particu' lar the" invention relates to safety glass whichis actinism-pr6of, or non-actinic.

While, fundamentally, the conception of W a laminated safety glass with one or more laminations of pyroxylin plastic is sound,.

the use of such glass as a colorless transpa'r'; ent Window is comparatively limited, chiefly for the reason that the strengthening layer of plastic material frequently becomes. col: ored or discoloredin the course of time, indicating deterioration, of which further evidence isthe' development of brittleness,

roughening, and crazing, often causing the glass to loosenfrom the plastic, and even sometimes breaking of the glass. Observation has indicated that this discoloration and decomposition of the plastic is due to the eifect'of actinic rays of the sun, e. g. ultraviolet light between2900and 4000 Angstrom units and principally. between 3200 and 3800 units. Various methods er overcoming this difficulty have been proposed but, for a variety of reasons, sucha's high'production ents are incorporated in the safety glass.

structure. These; ingredients may be, for example, beta-methyl umbelliferone, acetamino quinolin, aesculine, anethol, quinine sulphate, ferric chloride, potassium dich romate, nickel chloride in combination with aluminum chlo ide or calcium chloride, salts of certain me ls of high molecular weight such as cadmium, molybdenum, thorium, cerium,

uranium and others or various combinations of these. A variety of colors stable to sunlight and which, when compounded in an yellow,

n and blue, mayalso be used. These various ingredients may be used as circumstances diccost, and so on, have not. proved all that.

actinic-ray filtering stratum produce amber,

orange, as well as violet, red, green,

ncrmrsmrnoo'r nnnnroncnn GLASS.

' Application filed March 12, '1926. Serial No. 94,332.

tate," as explained more fully hereinafter.

The principle involved is that the ingredient used must becapable of reflecting or absorbing actinic light without objectionable deterioration or change in molecular strupture of any of the portions of the safety glass, as the ingredient itself, the strengthening sheet, the glass, or the vehicle carrying the ingredient. As an example of a reaction in accordance with this principle would be fluorescence, in which case the harmful a'ctinic rays are convertbed, into nonharmful rays. Another might e the absorption of the harmful' actinic rays, and the giving of them off in the form on nonharmful heat energy.

* In further and more particular accord a'nce with the invention, the ray-arresting ingredient is incorporated in the safety glass structure by way of a ray-filter stra-' tum built into the safety glass structure as an element initially distinct and separate ing layer of pyroxylin'plastic. That is to say, in safety glass of the present invention there'is usedfwith the glass layer and the strengthening layer, a layer which itself from the glass/proper and the strengthenconstitutes a, ray .screen, the ray-arrest1ng ingredient being embodied 1n the layer and the layer being of some material, as a thin sheet of gelatin or transparent pyroxylin5 plastic, in which the ingredient is easily incorporated. Among other advantages which this structure has are the following two, both important: All difliculties which Would-arise from attempting to incorporate the ray arresting ingredient in the glass proper or strengthening sheet are avoided; and the necegsity of incorporating thelarge amount of ingredient (some are quite expensive while others are harmful when incorporated) necessary to be distributed through the relatively thick strengthening layer in order to protect it in that manner, is avoided, while at the same time the,

ingredient can, by virtue of the thin separate sheet be concentrated at the surface-0i.

the strengthening sheet giving the maximum protection at the surface, as is, course, desirable. p

:Str'uctures embodying the invention may, of course, have various detail? characteristics,-such as the number of the layers, particular ray-arresting ingredient used, and so on. The ray screen may be initially-attached either to the glass or to the strengtheningsheet of pyroxylin plastic, or may be mad-gip as an initially separate layer, laid between the glass and the strengthening laye'r'and attached to them in the process of uniting the elements of the sandwich into a unitary whole. it may be desirable to mix the ray-arresting agent with a thin gelatin, pyroxylin, or other solution to,be sprayed on the glass or strengthening layer before, and to aid in. the uniting of the glass and strengthening layer, and in this Way provide the screen;

or a very thin previously-made sheet of pyroxylin, gelatin or other suitable material, containing the arresting agent, may be attached to the principal pyroxylin plastic sheet before such sheet, together with the glass, is assembled into the stack ready for compositing into the'sandwich. It will be understood that the embodying of the invention in the safety glass necessitates no departure from the usual and well understood methods of uniting the layers of the article, such methods embodying, in general, uniting the layers under heat and pressure supplemented if desired by heating gradually to initially soften the pyroxylin sheets, and so on, to facilitate the uniting of the layers as circumstances and convenience may dictate. As indicated above, the ray-arresting stratum may be of some other suitable bonding material than pyrcxylin, as gelatin, rubber, resinous materials, and so forth.

As an example of the practice of the invention, there may be used two sheets of glass of a desired thickness, a strengthening sheet of pyroxylin plastic approximately .020" thick therebetween, and a ray-filter stratum of pyroxylin plastic, gelatin, or other bonding material about .0005 to several thousandths of an inch thick between the strengthening sheet and one of the glasses: The strengthening sheet is made with sufiicient' color, of the necessary kind, to neutralize the color given to the screen by the addition of suflicient non-actinic ingredients to arrest the actinic rays of the sun. The color of the'strengthenjng sheet, therefore, depends upon the color of the filtering screen necessary to filter actinic rays.

The determining factor, as regards color,

is that the composite structure must be within the specifications for the particular use to which it is to be put. For exam le, if the product is to be used in automobile Windshields, or as a bullet proof glass in banks, it must berelatively clear and water qwhite, whereas if it is to be used for au t0 mobile yisors it must be' blue, amber or any other color specified. s

As a more specific example, not to be in- Thus', in certain cases.

terprete'd as a limitation as to the colors, ingredients, methods, etc.,' I have found a product, comprising a central strengthening sheet with a ray screen and a sheet of glass on each side, and made as. indicated below, to give very satisfactory results (1) Approximate composition of stren hening sheet .020" thick. (Parts by weig t.)

Parts.

Nitrocellulose 73 Gamphor 25 Volatile solvent (alcohol) 1. 5 Urea 5 Ultramarine 003 Violet lake .001

ters in the character of binding layers,- each .0005" thick. (Parts by, weight.) t

Gelatine 2.5 Water 97. 5

I (Vehicle for carrying actinic ray-arrest- (Germicida) (3) Glasses: each of ordinary plate glass composition ground to approximately,

thick.

(4) To composite, spray a binding layer on one side each of the two previously cleaned glasses and permit to dry. Place the strengthening sheet of pyroxylin plastic between the gelatin coated faces of the glass, heat the entire stack in a hydraulic press between felt pads to a temperature of approximately C., and press for 15 seconds with about 500 pounds of pressure per square inch on the glass. Cool in the press while pressure is maintained. (The press plates may be heated by circulating steam andcooled by circulating water.)

I also found that it is entirely practical to use a ray filter or binding solution on one glass containing, say, twice the indicated amount of non-actinie ingredients, and a binding solution on the other glass containinga less amount of non-actinic ingredients, thus to afford more protection on one side, i. e. that that is to be exposed to the sun than onthe, other. This method is .found advisable particularly for outdoor use where the said other side is protected by facing an enclosure; but it cannot be used to good advantage for indoor use or outdoor use where both sides are exposed equally to the actinic hght. The strengthening sheet may be made by any of the regular methods of making py (2) Approximate composition of ray filroxylin plastic sheets, as may also the filter layer when provided as,a previously-made initially separate sheet of yro-gzylin plastic.

Evidently many types 0 structure may be made without departure from the invention;

as structures with but one glass, or structures comprising a central glass (preferably about twice as, thick as the outside glass) with, ,in order on each side, eithera lain or a ray-arresting bindin sheet of ge atin or the like, a strengthening sheet, a binding sheet in the character of a ray-filter, and a sheet of glass; also a filter of one specific character may be used on one side, and a filter of a different specific character-may. be used on the other, and in this Way any' iobjectionable cdlorin one can be counteracted by the other. Also, the ray-filter sheet need not necessarily be an interior layer, although I prefer it to be so. v i Q Although the intention has been described with more particular reference to a product embodying a strengthening layer ofpyroxylin plastic, it will be understood, of course,

that it may find ap lication :in products in which the layer-lia le to deteriorate is of material other than p o lin, forexample, cellulose acetate,'ethy ce u lose, etc.

I claim: 'g 1 As an article of manufacture, a reenforced glasej structure conzprising a sheet of glass, a}lay'e'r of materi of material which tends to which tends to change color when sad to actinic rays of light, and a ray-filter ayer.

2. As an article of manufacture, a reenlight, and a layer of material havmgincorporated therein and t distributed therethrou h an actinism-proofingsubstance.

5. s an article of manufacture, atreen forced glassstructurecomprisin a sheet of glass, alayer, of material whigi tends to change color when exposed to actinic'rays of light, and a layer of film-for material havin incorporated therein and ributed theret ough an actinism proofing-* sub- Stance. a V. ,7

6. As an article of manufacture, a reenforced glass structure comprising, in order, a sheet of glass, a'ray-filter layer and a la er hange co or when exposed to actim'c rays of light. In testimony whereof I afiix my signature.

- i 7 JAMES H. SHEETS pyroxylin plastic, and a 

